People like the one you describe thrive in a culture that is blinded by its reflexive urge to support its officers in the face of the nature of the work.
I'm talking about how the abstract concept of these jobs inherently contains the seeds of their inhumanity. If that is fixed the many who are abusive can be seen clearly by each other. You rightly point out that there are individuals carrying out a far worse sociopathy than even the job could dream up for them. I completely agree.
I'm not saying your idea of the situation doesn't happen, but there are a good number of already unstable people seeking out the job, long before they have a chance to be altered by it.